The objective is to assess efficacy and safety of Acetylcysteine/Doxofylline 1200/400 mg Effervescent Tablet once daily treatment besides standard/usual treatment, as compared with placebo once daily in patients with stable moderate to severe COPD.

The objective is to assess efficacy and safety of Acetylcysteine/Doxofylline 1200/400 mg Effervescent Tablet once daily treatment besides standard/usual treatment, as compared with placebo once daily in patients with stable moderate to severe COPD.

Patients who met all inclusion criteria will be randomized to receive double-blind treatment with Acetylcysteine/Doxofylline 1200/400 mg Effervescent Tablet once daily (n = 35) or placebo (n = 35) once daily for 4 weeks.

Patients will be evaluated at 2 consecutive visits: screening & treatment visit (first visit) and after treatment visit (second visit).

Spirometric measurements will be performed at pre-treatment during the first visit and post-treatment at two different time points (23 hr + 15 min and 23 hr + 45 min) during the second visit. The average of the values at 23 hr 15 min and 23 hr 45 min during the second visit will be defined as trough value.

Inclusion Criteria:

• Patients aged ≥40 years with moderate-severe COPD diagnosis according to the GOLD and on a therapeutic regimen for COPD for a year
• Patients with post-bronchodilator FEV1/FVC ratio <0.70
• Patients with post-bronchodilator FEV1≥30% and <80% of predicted normal value.
• Current smokers or ex-smokers with a smoking history of at least 10 pack-years
• Patients who have no exacerbation within last 4 weeks
• Females patients with childbearing potential using effective birth control method
• Patients who have a capability of communicate with investigator
• Patients who accept to comply with the requirements of the protocol
• Patients who signed written informed consent prior to participation

Exclusion Criteria:

• History of hypersensitivity to drugs contain Acetylcysteine or Doxofylline or other mucolitics or xanthines
• Patients who use mucolitic and/or xantines derivatives or ephedrine routinely.
• Patients who use CPAP (continous positive airway measure), BiPAP (bilevel continous positive airway measure) or mechanical ventilation
• History of chronic respiratory diseases except COPD.
• Patients who had COPD exacerbation or lower respiratory track infections that required antibiotic, oral or parenteral corticosteroid treatment within 4 weeks prior to first visit.
• Patients who have a history of myocardial infarction, hearth failure, acute ischemic coroner disease or severe cardiac arrhythmia requiring treatment within least 6 weeks.
• History of significant or uncontrolled disease or operation that may preclude participant from participating in the study
• Patients who have lung cancer
• Patients who had lung volume reduction operation
• Women patients who are pregnant or nursing
• History of allergic rhinitis or atopy
• Patients who have known serious prostatic hypertrophy or narrow-angle glaucoma requiring drug therapy
• History of alcohol abuse.